The present installation relates to cable transport systems in which a closed loop formed of a carrier-tractive cable or tractive cable travels over a first pulley and a second pulley, one at least of these two pulleys driving and being driven by a motor controlled by a control means. In known installations, the shaft of the first pulley is fast with a first fixed frame of the installation and the shaft of the second pulley is retained by a second fixed frame of the installation at a distance from the first fixed frame. Transport members are attached to the cable to be driven by said cable between the first fixed frame or first station and the second fixed frame or second station of the installation.
Cable installations are often used for transporting passengers, particularly in mountain regions, and comprise a lower station and an upper station, the stations being remote from each other. The distances frequently met with often exceed 500 to 1000 meters. During use of the installation, the cable is subjected to relatively high temperature variations, which may produce not inconsiderable length variations. In addition, the cable is subjected to relatively high tractive forces, which may cause progressive creep under tensile stress in time, mainly at the beginning of the period of use of a new cable.
So that installations may maintain more or less constant tension of the cable, despite the progressive creep of the cable in time and the temperature variations, use is very often made of a counterweight. In this case the shaft of the second pulley is mounted on a carriage which is mobile with respect to the second fixed frame and retained by a counterweight.
In some recent installations, the counterweight has been replaced by jacks or self-acting jacks for regulating the cable tension and thus fulfilling the same functions as a counterweight.
Such known installations however have numerous drawbacks and particularly:
very often the counterweight is made from concrete or other different materials and its weight is never known accurately;
during operation, the dynamic effects due to the inertia of the counterweight or the means controlling the jack create sometimes overloads and sometimes uncontrolled underloads;
the pressures for driving the jacks are difficult to control, particularly under dynamic operating conditions;
the means for controlling and driving the jacks lack rapidity and thus create uncontrolled dynamic effects;
installations with counterweights or jacks require relatively complex mechanical elements which substantially increase the cost of the installation.